Science Buddies: "Ask an Expert"

(Sorry if I posted this question in the wrong forum. )I For my annual Science Fair Project I conducted the Forensic Science: Building you own tool for identifying DNA project. The experiment was a success, but I just had a few questions about the results. I used the food coloring dye colors blue,yellow, and green. First of all, I was wondering if there was a reason why green "ran" the farthest in the experiment? Does green just have smaller macromolecules? If so, what would make that occur? Secondly, I saw that during and after the experiment there were copper bubbles at the positive end of the box. What are these bubbles, and why were they just at the positive end and not the negative end too? Lastly, I noticed that about 24 hours after the experiment ended the separated colors, while still in the gel, had darkened and spread. Why did they do this? Thanks, and I would appreciate any and all feedback!

Hi LoverOfScience1234,
Those are some very good questions. In regards to why green ran the farthest, it seems to me that what you have suggested is on the right track. Please review the wikipedia link from the project page for the additional information. (Specifically, please review the 2nd paragraph under the "SEPARATION" heading.)
http://en.wikipedia.org/w/index.php?tit ... =195457494

In regards to the copper bubbles, would you happen to have any pictures that you can share / upload to the site?

Thanks!
Willey

Thank's very much for your help Willey! I really appreciate the feedback! The link you provided was very helpful. I was just wondering if there was a really specific reason why green's molecules would have a smaller mass? Is that just the way it is or does it have something to maybe do with the fact that green is the only secondary color?
As for the copper bubbles, I attempted to upload the picture the website said "The extension page is not allowed." However, the same copper bubbles were in the video of this experiment science buddies provided on youtube. Here is the link.
https://www.youtube.com/watch?v=QWkfXjGohVk.
The "bubbles" were at the very end where the two girls show the results on a plate. The "bubbles are imprinted in the gel.
Lastly, as for the smearing and darkening I spoke of in my first post, I am still wondering what that could be a result of. The best way I can describe that without a picture would be that after leaving the gel in the plastic box, which was in a plastic bag, after 24 hours (at room temperature) the gel had drastically changed. The colors have all blended together. There is absolutely no clear gel left in the plastic box. Most of the gel changed to a reddish brown color. What caused this? After the 24 hours no other change occurred.
I had one more question about the results. I understand why green separated into blue and yellow, but why did blue separate into blue and red? Also, why did yellow just separate into more yellow while no other color stayed the same?
Thanks in advance for any feedback you can provide!

Hi LoverOfScience1234,

Willey has given you some really great advice. I just wanted to chime in with some thoughts about your later questions.

As far as the mass of the green dye molecule goes, I doubt that its smaller molecular mass is related to the fact that green is a secondary color in subtractive color theory. The size of the molecule is the critical factor.

I suspect the "bubbles" are related to redox reactions between the cooper and gel.

As for the smearing and darkening you observed, the dye molecules will diffuse through the gel even in the absence of a driving potential. For example, think about what happens when you put a drop of food coloring into a glass of pure water. Even if you didn't stir the water and the water were perfectly still to begin with, over time the dye will diffuse through the water, turning the entire glass of water the color of the food coloring. The process you are seeing in the gel is analogous. All of the dyes diffuse, so the final color you observe is the result of mixing together all of the dyes. You can test this by putting the same number of drops of green, red, and yellow food coloring in a glass of water as you put into the gel, and then letting the glass of water sit undisturbed for several hours.

Finally, the separation of blue into red and blue tells you that the shade of "blue" food coloring you tested is actually a mixture of a red dye and a blue dye. The fact that yellow did not separate into other colors indicates that the yellow food coloring has only 1 dye molecule.

Thank you so much for answering my questions Terik!